KR100535339B1 - Reproduction method of tin solder collected by using waste solder - Google Patents

Abstract

The present invention relates to a method for recovering tin (Sn) by electrolytic refining a waste solder. Then, the tin (Sn) is installed as a negative electrode and then electrolyzed in an electrolyte solution so that the tin (Sn) eluted from the positive electrode (waste solder) precipitates with high purity (99.9%) on the negative electrode surface. It is easy to recover.

Description

How to recover tin from waste solder {REPRODUCTION METHOD OF TIN SOLDER COLLECTED BY USING WASTE SOLDER}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering tin (Sn) by electrolytically purifying waste solder, wherein an agglomerated waste solder is used as an anode, and tin is used as a cathode. Electrolytic refining (electrolytic refining) in the solution to allow the tin eluted from the positive electrode (waste solder) to be deposited on the negative electrode surface to recover high purity (99.9%) of tin.

With the advancement of the industry, the production of electronic products has increased, and the rapid development of related industries has shortened the life of the products. As a result, a huge amount of waste electronic products are generated each year, and most of them are printed circuit boards ( PCBs or PWBs, Printed Circuit [Wiring] Boards) are included.

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Soldering is a technology that joins high melting point metals with low melting point alloys. In particular, soldering is widely used for mounting various electronic components such as semiconductor chips, resistors, and capacitors in printed circuit boards. Foreign materials and impurities are mixed from the printed board or the surroundings by repeated use, and then discarded after a predetermined time or a predetermined number of times of soldering.

As the soldering material, tin (Sn) (60% to 70% wt) and lead (Pb) (30% to 40% wt), which are easy to handle and melt at low temperatures, are mixed as a main material, and other materials such as flux This several% (wt) mixed solder is used.

When disposing or embedding a printed circuit board manufactured using the solder, lead (Pb) in the solder flows into the groundwater and contaminates soil and rivers, and also has a huge adverse effect on various living organisms. This is following. Accordingly, in recent years, tin (Sn) is mixed in a weight ratio of 90% or more instead of lead (Pb) as a soldering material, and silver and / or copper and other mixtures of less than 10% by weight are used.

Tin is an element symbol Sn, atomic number 50, atomic weight of 118.70, specific gravity of 7.3, melting point of 232 DEG C, which is a white flexible metal that is stable and easy to process in air, and is made of bronze, fusible alloy, and bearing alloy. It is used as a soldering material, and is particularly popular as a soldering material due to its excellent malleability and ductility.

On the other hand, Pb, whose use is regulated due to its harmfulness, has an atomic weight of 207.19, specific gravity 11.3437 (16 ° C), melting point 327.4, boiling point 1,750 ° C, color is off-white, crystals are equiaxed crystals, and solubility is dissolved in nitric acid and concentrated pyrosulfuric acid. In nature, mainly zinc sulfide and lead sulfate (PbSO ₄ ), white lead (PbCO ₃ ), sulfur lead [PbCl ₂ · ₃ Pb ₃ (AsO ₄ ) ₂ ], graphite ore [PbCl ₂ · 3Pb ₃ (PO ₄ ) ₂ ] or the like.

The lead (Pb) is acute lead poisoning by inhalation and oral ingestion symptoms such as vomiting, stomach cramps, and when accumulated in the human body becomes a chronic poisoning state.

The main lead (Pb) compounds include lead monoxide (PbO), lead dioxide (PbO ₂ ), lead trioxide (Pb ₃ O ₄ ), lead chloride (PbCl ₂ ), lead sulfide (PbS), and lead nitrate (Pb (NO ₃ )). ₂ ), basic lead carbonate ((PbCO ₃ ) ₂ ㆍ Pb (OH) ₂ ), lead sulfate (PbSO ₄ ), lead acetate ((CH3COO) Pb ₂ 3H ₂ O), lead chromate (PbCrO ₄ ), lead thiocyanate (Pb (SCN) ₂ ), calcium lead acid (Ca ₂ PbO ₄ ), and most of them cause chronic toxicity.

The chronic toxicity includes boredom, weight loss, but the main symptom is anemia. This is due to the shortening of red blood cells and lead to inhibition of hemoglobin synthesis. Gastrointestinal disorder is the second most common symptom after anemia, including anorexia, constipation, and colic. Colic seizures are a risk of rapid onset over the long term, and peripheral nervous system and motor system disorders are many nerve palsy of the fingers.

Central nervous system symptoms include headaches, dizziness, insomnia, nervousness, etc., and encephalopathy in children has a high mortality rate and even after survival, 25% of them remain sequelae. Lead also accumulates in the aorta, and its objective relationship has not been established, but the rate of arteriosclerosis is high in workers exposed to lead. In addition, it is easy to cause chronic gastrointestinal disorders, in particular, symptoms such as visual impairment, hearing impairment, dysmenorrhea have been reported.

If you look at the regulatory standards for lead (Pb) in Korea, the average of three months of air environmental standards below 1.5㎍ / ㎥, the water quality standards below 0.1mg / ℓ (river, lake, sea area), 10mg / S in the Air Quality Preservation Act It is regulated to less than 3m3, and less than 0.2mg / l in clean areas under the Water Quality Preservation Act, and mixed with lead compounds (except lead tetraoxide, lead sulfate, and basic lead carbonate) and more than 25% in Hazardous Chemicals Control Act. Substance and soil environmental conservation law is 100 mg / kg for agricultural land, 400 mg / kg for factory and industrial area, 300 mg / kg for agricultural land, 1,000 mg / kg for factory and industrial area, 3 mg / in waste management method. It is regulated to be more than l (eluate), 0.1mg / l or less for drinking water quality standards, and 0.1mg / l or less for living water quality standards (living water, agricultural water, industrial water).

Conventionally, binary process alloys made of tin (Sn) and lead (Pb) are mainly used as soldering materials for mounting electronic components on printed circuit boards. In recent years, development of environmentally friendly lead-free alloys has been actively conducted by restricting or excluding lead in manufacturing alloy solders.

On the other hand, solder containing 90% or more of tin by weight instead of hazardous lead (Pb) and silver and / or copper and other materials of less than 10% by weight may be repeatedly printed or Since foreign matters and impurities are mixed therein and the quality thereof is deteriorated, efficient regeneration is not necessary when a predetermined time or a predetermined number of times is used.

Therefore, in the present invention, the waste solder in the form of agglomerated waste is used as the positive electrode, and the tin (Sn) as the negative electrode is electrolyzed in the electrolyte solution to elute from the positive electrode (waste solder). It aims at making it possible to collect | recover high purity tin (Sn) by making it precipitate on this cathode surface.

In order to achieve the above object, tin (Sn), which occupies most of the waste solder, is eluted using electrolytic refining to precipitate and recover to the cathode surface so that it can be reused as a solder. . Of course, the solder is mostly tin and lead free.

In addition, there is provided an electrolytic cell containing an electrolyte solution and an electrolytic power supply for supplying a power source required for electrolysis to the waste solder (anode) and tin cathode immersed in the electrolyte solution and the waste solder and cathode. Characterized in that, the electrolytic power source is preferably using a direct current power source rectified by a commercial AC power supply rectifier.

In describing the present invention, the same components in the drawings are denoted by the same reference numerals as much as possible, and detailed descriptions of related known configurations or functions will be omitted so as not to obscure the subject matter of the present invention.

1 is an electrolytic purification reference diagram of an embodiment of the present invention, and FIG. 2 is a state diagram in which tin (Sn) is deposited on the cathode surface by electrolytic purification.

The tin (Sn) recovery apparatus used as an example of the present invention comprises an electrolytic cell 2 containing a predetermined amount of an electrolyte solution 1 and a waste solder 4 in a lump state immersed in the electrolyte solution 1. A positive electrode (+), a negative electrode (-) (3) consisting of a planar tin plate material and an electrolytic power source (5) for supplying power for electrolysis to the positive electrode (+) and the negative electrode (3) is provided, The electrolytic power source 5 preferably uses a DC power source rectified by a commercial AC power source (AC 220V) with a rectifier.

The tin (Sn) recovery device varies in size and capacity depending on the processing capacity and the like.

In the electrolytic refining of the present invention, a tin plate material composed of a target metal such as tin (Sn) is used as a positive electrode (+) using the waste solder (4) in the form of agglomerate mainly containing tin (Sn) as a crude metal. An electrolyte solution (1) and an electrolytic power source (5) are used so that the tin (Sn) can be easily eluted from the crude metal.

In the electrolyte solution (1), sulfuric acid (H ₂ SO ₄ ) and silicic acid (H ₂ SiF ₆ ) are 58% to 68% and 40% to 30% by weight so that an appropriate aqueous solution of salt can be electrolyzed. It is mixed and other additives are mixed in small amounts (2% by weight).

In addition, in the present invention, an acid resistant chemical heat transfer heater (not shown) is installed in the electrolytic cell 2 to induce a rapid chemical reaction.

The heat transfer heater is comparatively controlled by a controller (not shown) and a reference temperature set by a temperature sensor (not shown) and a temperature setting unit installed to be immersed in the electrolyte solution (1), and the electrolyte solution (1) by the controller The temperature of is maintained at a constant temperature of 60 ℃ ~ 80 ℃, thus a more effective and fast chemical reaction is made to improve the productivity more.

Since the constant temperature method and the controller are technologies widely used in other industries, detailed descriptions or illustrations will be omitted.

In the present invention, since the main purpose is to recover pure tin from the waste solder 4, which is mostly tin, the waste solder 4 corresponding to the crude metal is used as the positive electrode (+), and the planar tin end plate ( I) If the cathode is composed of the negative electrode (-), 99.9% of pure tin (Sn) continues to precipitate on the negative electrode 3 surface (cathode surface) as shown in FIG. 2, and the waste solder 4 almost elutes. When disappeared, most of the pure tin precipitates to the cathode 3 surface. When the precipitation of tin is completed or when the tin is appropriately recovered, the cathode 3 is pulled out of the electrolytic cell, and the tin stuck to the surface of the cathode 3 can be effectively separated and recovered by using a tool or the like. Used as a solder material, resources can be recycled.

In electrolytic purification in the present invention, an element that is electrochemically more stable than the target tin in the impurities remains without eluting at the positive electrode (+), and the element unstable than the desired tin is eluted together but does not precipitate as the negative electrode (3). Instead, they remain in the electrolyte solution 1 and are separated, so that the tin precipitated as the negative electrode 3 becomes high purity (99.9%). And, by remaining in the electrolyte solution (1) by electrolysis or settled to the bottom of the electrolytic cell (2), it may be removed separately.

In the present invention, in order to increase the purity of tin eluted from the anode, since they may be precipitated together with tin, it may also be a method of removing by dry purification in advance.

In the present invention, since 99.9% of high-purity tin can be recovered and reused from the waste solder 4 using the electrolytic refining method, resources can be reused. The time is not particularly limited. Then, a sufficient time may be given depending on the concentration or type of the electrolyte solution 1.

Reference numeral 6 denotes a power switch capable of energizing or turning off the electrolytic power source 5 as necessary.

The present invention described above is not limited to the above-described embodiment and the accompanying drawings, and it is understood that various forms of substitution, modification, and alteration are possible without departing from the technical spirit of the present invention described in the claims. It will be apparent to those of ordinary skill in the art.

As described above, the present invention is capable of refining and recovering tin in a waste solder (waste solder) discarded after being used in an electronic product assembly process with high purity of 99.9%. It is a useful invention with the effect of being friendly and hardly generating sludge.

1: Reference diagram of electrolytic purification of an embodiment of the present invention.

2: reference diagram of a state in which tin (Sn) is deposited as a cathode in FIG. 1.

<Explanation of symbols for main parts of the drawings>

(1)-electrolyte solution (2)-electrolyzer

(3)-cathode (tin cathode) (4)-waste solder (anode)

(5)-electrolytic power

Claims (3)

In the method of electrolytic recovery of waste solder; 99.9% of the tin was deposited by depositing the waste solder anode and the tin plate anode made of tin in the electrolyte solution of the electrolytic cell and electrolytically dissolving with the electrolytic power to precipitate the tin eluted from the waste solder on the tin plate cathode surface. Recovering tin from the waste solder, wherein the tin is recovered. delete The method according to claim 1; The electrolyte solution is characterized in that sulfuric acid (H ₂ SO ₄ ) and silicic acid (H ₂ SiF ₆ ) is mixed in a weight ratio of 58% to 68% and 40% to 30%, and other additives are mixed in a small amount by weight ratio Recovering tin from waste solder.